Two of China's mobile carriers have cut the cost of iPhone contracts as the country's largest carrier adds the phone to its lineup.

Following years of negotiations, Apple and China Mobile finally announced an agreement last month to sell the two new iPhones starting January 17. With a subscriber base of 760 million subscribers, China Mobile is, by far, the nation's biggest mobile carrier.

So it's no coincidence that rivals China Telecom and China Unicom are taking steps to retain their grip on the market.

China Mobile has yet to reveal prices for the iPhone and its long-term contracts. An unsubsidized iPhone 5S starts at 5,288 yuan ($873), while an off-contract 16GB 5C goes for 4,488 yuan ($741). Piper Jaffray analyst Gene Munster recently forecast that China Mobile could sell as many as 17 million iPhones this year, around 2 percent of its total subscriber count.